1. Field of the Invention
The present invention relates in general to magnetic recording tape cassettes and more specifically to a rotatable tape roller guide for such cassettes.
2. Description of the Prior Art
Typical tape cassettes include a case with spaced apart sidewalls, at least one tape supporting reel rotatably disposed between the case sidewalls, and a pair of tape guiding members which are typically pin mounted in the case. Rotatable tape roller guides in tape cassettes are advantageous because they produce minimal drag on the tape and thereby reduce the torque required to advance the tape. However, in the past it has been a problem to efficiently and economically produce cassettes including rotatable guides having proper bearing end clearances. If too small a bearing end clearance is provided, the guides will bind in the case; if too large a bearing end clearance is provided, the guides will oscillate on their pin shafts and when driven at high speeds produce an irritating noise. A lowering of the quality of reproduction of the recorded format due to improper tape positioning as a result of such oscillation can also occur.
Attempts to provide the required case to roller guide clearance while limiting oscillation have been disclosed in U.S. Pat. No. 3,891,159, issued June 24, 1975 to Nelson, and U.S. Pat. No. 3,829,040 issued Aug. 13, 1974 to Nelson, both assigned to the assignee of the present invention, which show shim layers positioned within the cassette body which straddle the roller guides to prevent oscillation and a spindle press fitted into the roller guide bore and adjusted by contact with the case as the cassette case is assembled, respectively.
Another means for preventing guide oscillation was shown in U.S. Pat. No. 3,735,940 issued May 29, 1973 to Schwartz in which a roller is shown biased into contact with the cassette case by a coil spring.
Although these methods of preventing roller guide oscillation have proven to be operationally satisfactory, they result in undesirable manufacturing expense and assembly costs.